High-silicon steel rails



April 15, 1958 .J. R. ZADRA 2,330,397

HIGH-SILICON STEEL RAILS Filed April 15, 1955 STANDARD CARBON RAIL-"STEEL HI-SILICON RAIL STEEL" WORN AREA 0.22 WORN AREA 0.29

r-u-snucon RAIL STEEh STANDARD CARBON RAIL SILEEL WORN AREA 0.15 WORN AREA 0.42

INVENTOR JOHN R. Z ADRA United States Patent Fuel & Iron Corporation, Denver, (3010., a corporation of Colorado Application April 15, 1955, Serial No. 501,581

1 Claim. (Cl. 75-123) This invention relates to steel railroad rails, and has for its object the provision of steel rails having improved mechanical properties attained by the incorporation of a relatively high percentage of silicon in certain carbon rail steels. The improved rails of the invention have exceptional resistance to wear, reduced flow properties and gage corner shelling, good adhesion between the wheels and the rails, increased strength, and are free of brittleness.

During an extensive investigation I have confirmed the surprising fact that an appreciable increase in the silicon content of rail steel very greatly increases the service life of the rails. My invention is based upon a rail steel composition comprising from 0.50% to 1.00% of silicon, preferably from 0.55% to 0.65% of silicon, carbon varying from 0.67% to 0.85%, manganese varying from 0.70% to 1.00%, and with phosphorous and sulfur in the amounts common to rail steels. It is important that the carbon content be relatively high but below the eutectoid point which is around 0.85%. I have found that I can increase the silicon content of rail steel very appreciably and the resulting silicon is in solution in the iron with a resulting great increase in the wear resistance and other properties of the rails without causing brittleness. Although it was known that silicon forms a solid solution with iron, being dissolved in both the iron carbide plus ferrite and the free ferrite, it was the prevailing belief, exemplified by the setting of rail steel composition standards, that the silicon content should not be increased above about 0.23%. Heretofore, the only reason for adding silicon to rail steel was for the purpose of deoxidation. The rails which have been standardized by the American Railroad Engineering Association (AREA) and which are used by all the American railroads contain only a sufficient amount of silicon to assure deoxidation. The AREA standard carbon steel analyses is given in Table I. By increasing the silicon content of the steel quite appreciably toform a solidsolution alloy with the alpha iron (iron-silicon), I thereby strengthen the iron without causing brittleness. The strengthening effect of the alpha iron (ferrite) is due to improved mechanical properties which tend to increase resistance to plastic flow of the metal, thus achieving retardation of the rapid development and propagation of gage corner shelling, as well as greatly improved rail wear.

The following are the analyses of standard carbon .AREA rail steel and the high-silicon rail steel analyses of the invention:

2,830,897 Patented Apr. 15, 1958 Certain rails having the steel analyses of the foregoing table showed the following mechanical properties:

Brinell Tensile Yield Reduc- Endur Hard- Strength, Strength, Elong. tion of ance ness p. s. i. p. s. i. in 2" Area Limit, p. s. 1.

Standard Carbon Steel Rail 255 129, 000 65, 500 8. 2 17.0 62,000 High-Silicon Steel 119.11.... 285 146, 000 83, 600 8.8 14. 7 64, 250

Under the heavy loads of present railroad traflic the rail-head metal sufiers from excessive plastic flow and wear. During recent years the rail defects known as gage corner shelling and detail fractures from shelling have become a serious problem. The wheel loads are too heavy for the small area of contact between the wheel and rail and this results in the plastic flow of railhead metal, producing internal stresses which exceed the capacity of the steel to withstand the stresses. Many failures have been due to abnormal shearing stresses imposed on the gage corners of rail-heads. The high silicon steel rails of my invention practically overcome, or at least effectively decrease, these rail drawbacks.

In the accompanying drawings actual cross-sections of rail-head contours are shown after service on a section of railroad having a 9 8" curve and 3 inch elevation, in which: i

Fig. 1 shows the head of a low rail composed of standard AREA carbon steel;

Fig. 2 shows the head of a low rail having the steel composition shown in Table I;

Fig. 3 shows the head of a high rail having the steel composition shown in Table I; and

Fig. 4 shows the head of a high rail composed of standard AREA carbon steel.

The rail sections shown in Figs. 1 to 4 are accurate contours taken from rails in service which have had many millions of tons of traffic. The full line contours show the shapes of the original new rails, and the broken line contours show the contours of the worn rails.

The rails of Figs. 1 and 2 were under the greatest load because of their lower positions on the curves. Not only did the carbon steel rail of Fig. I wear more than the high-silicon steel rail of Fig. 2, but the plastic flow is very much greater in the carbon steel. The area of wear of the rail of Fig. l was 0.22 square inch while the area of wear of the rail of Fig. 2 was 0.15 square inch.

The rails of Figs. 3 and 4 were located on the high side of the curve and were under a lower load than the lower rails of Figs. 1 and 2, but they were subjected to much greater wheel wear due to lateral load on the gage side of the rail head. While there is evidence of plastic flow in the carbon steel rail of Fig. 4 there is no evidence of plastic flow in the high-silicon steel rail of Fig. 3. The absence of plastic flow results in the retardation of the rapid development and propagation of gage corner shelling as well as eminently improved rail wear. The worn area of the rail of Fig. 3 was 0.29 square inch which is clearly much less than is the worn area of the rail of Fig. 4 which was 0.42 square inch. Calculations of the rates of wear based on the respective worn areas of the rails of Figs. 3 and 4 indicate a very appreciable improvement in the rail life of the high-silicon rail steel.

In comparative rolling load tests carried out in a laboratory on samples of actual rail sections to produce gage corner shelling it was shown that the high-silicon steel rails of this invention withstand on the average about two and one-half times the number of cycles before failure than standard carbon steel rails.

3 4 Table II gives the composition of typical highsilicon Carbon from 0.67% to 0.85 steel rails which are subjected torol-ling load tests. Manganesefrom 0.70% to 1.00%

Silicon from 0.50% to 1.00% TABLE II Phosphorus not over 0.040% Steel analysis 5 Sulfur not over 0.070%

Remainder, iron.

0 Mn Cycles I claim:

Failure Railroad rails the steel of which comprises from 0.67%

S l Si before I to 0.85% of carbon, from 0.70% to 1.00% of manganese,

8 8,28 0,33% 8%? 228 888 from 0.55% to about 0.65% of silicon, not over 0.040% 0 021 0:025 8: 60 21111000 phosphorus, not over 0.070% sulfur, and the remamder 0.78 0.89 0 021 0 025 0.00 2, 225, 000 substanfilally all H011- M References Cited in the file of this patent iii The standard AREA carbon steel rails fall after an UNITED STATES PATENTS average of about 1,000,000 cycles while the high-silicon 1,661,176 Gink Mar. 6 1928 rails withstand from two to three and one-half times the 1382115 Brunner Oct 1932 number of cycles before failure. I v u The improved high-siliconstecl rails ofgthe invention 20 OTHER REFERENCES consist essentially of the following: Metal Progress, vol. 20, November 1931, page 40. 

